Radiation imaging apparatus

ABSTRACT

A radiation imaging system is equipped with a radiation imaging apparatus and a control apparatus. The radiation imaging apparatus reads out image signals from a radiation detecting section that detects radiation which has passed through a subject, and outputs the read out image signals as wireless signals. The control apparatus outputs predetermined control signals to the radiation imaging apparatus as wireless signals. A second wireless communicating section of the control apparatus decreases the signal strength of communications to be lower during readout of the image signals than at times other than during readout of image signals.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority from Japanese Patent ApplicationNo. 2007-251180, filed Sep. 27, 2007, the contents of which are hereinincorporated by reference in their entirety.

FIELD OF THE INVENTION

The present invention is related to a radiation imaging system equippedwith: a radiation imaging apparatus that reads out image signals from aradiation detecting section that detects radiation which has passedthrough a subject and outputs the image signals as wireless signals; anda control apparatus that outputs predetermined control signals to theradiation imaging apparatus as wireless signals.

DESCRIPTION OF THE RELATED ART

Various radiation detectors that record radiation images of subjectswhen irradiated by radiation which has passed through the subjects havebeen proposed and are in practical use in the field of medicine and thelike.

For example, there are radiation detectors that utilize semiconductorssuch as amorphous selenium that generate electrical charges whenirradiated by radiation. Radiation detectors of this type that employthe so called optical readout method and the TFT readout method havebeen proposed.

Japanese Unexamined Patent Publication No. 2006-247102 discloses aradiation imaging system that employs the aforementioned radiationdetector, equipped with: a radiation imaging apparatus that reads outradiation image signals from the radiation detector and outputs theradiation image signals as wireless signals; and a control apparatusthat outputs predetermined control signals to the radiation imagingapparatus as wireless signals.

Radiation image signals which have been read out from a radiationdetector are output as wireless signals in the radiation imaging systemof Japanese Unexamined Patent Publication No. 2006-247102. If radiationimage signals which have already been read out are output as wirelesssignals during readout of new radiation image signals from the radiationimage detector, noise will occur within the radiation image signalswhich are currently being read out, due to influence of the radio wavesof the wireless transmission, resulting in deteriorated image quality ofthe radiation image. This is because the radiation image signals whichare read out from the radiation image detector are extremely weaksignals.

Therefore, the operation of a communications module of the imagingapparatus that outputs wireless signals is ceased during readout ofradiation image signals from the radiation detector, in the radiationimaging system disclosed in Japanese Unexamined Patent Publication No.2006-247102.

Japanese Unexamined Patent Publication No. 2003-210444 also discloses aradiation imaging system equipped with an imaging apparatus and acontrol apparatus. In this radiation imaging system, a directionalantenna is used to output wireless signals such that radio waves are notirradiated onto a radiation image detector and a detecting section thatreads out radiation image signals from the radiation image detector, inorder to suppress the aforementioned adverse influence imparted by thewireless signals.

The radiation imaging systems disclosed in Japanese Unexamined PatentPublication Nos. 2006-247102 and 2003-210444 consider only the adverseinfluence imparted onto the radiation image signals, which are beingread out, by the wireless signals output by the imaging apparatus.

There is a possibility that adverse influence may be imparted ontoradiation image signals, which are being read out, not only the wirelesssignals output by the imaging apparatus, but also by the wirelesssignals output by the control apparatus. The adverse influence mayresult in noise entering the radiation image signals which are beingread out, leading to deterioration of image quality.

SUMMARY OF THE INVENTION

The present invention has been developed in view of the foregoingcircumstances. It is an object of the present invention to provide aradiation imaging system, which is capable of suppressing the adverseinfluence imparted by wireless signals output from a control apparatusonto radiation image signals, which are being read out.

A radiation imaging system of the present invention comprises:

a radiation imaging apparatus, comprising:

-   -   a radiation detecting section that generates electric charges        when irradiated with radiation which has passed through a        subject, to record a radiation image of the subject;    -   a readout section that reads out image signals that represent        the radiation image of the subject from the radiation detecting        section; and    -   a first wireless communicating section that reads out the image        signals from the readout section and outputs the read out image        signals as wireless signals; and

a control apparatus, comprising.

-   -   a second wireless communicating section that receives the        wireless signals output by the radiation imaging apparatus, and        outputs predetermined control signals to the radiation imaging        apparatus as wireless signals;

the second wireless communicating section decreasing the signal strengthof communications during readout of the image signals by the readoutsection to be lower than the signal strength of communications at timesother than during readout of image signals.

In the radiation imaging system of the present invention, the secondwireless communicating section may:

set the signal strength of communications to a degree that enablescommunication between the radiation imaging apparatus and the controlapparatus;

decrease the signal strength of communications in a stepwise manner, toobtain a signal strength at a step which is greater than or equal to aminimum signal strength that enables communications between theradiation imaging apparatus and the control apparatus; and

set the obtained signal strength as the signal strength ofcommunications during readout of the image signals.

Alternatively, the second wireless communicating section may set thesignal strength of communications during readout of the image signals toa degree at which the wireless signals output from the second wirelesscommunicating section do not influence the image signals which are beingread out.

Here, the term “during readout” refers to a period of time during whichelectric charges which are generated in the radiation detecting sectiondue to irradiation by radiation are being read out as image signals.

In addition, the phrase “a degree at which the wireless signals outputfrom the second wireless communicating section do not influence theimage signals which are being read out” refers to a signal strength atwhich no noise occurs in the image signals being read out due to thewireless signals, or to a signal strength at which a negligible amountof noise occurs in the image signals.

In the radiation imaging system of the present invention, the secondwireless communicating section of the control apparatus decreases thesignal strength of communications during readout of the image signals bythe readout section to be lower than the signal strength ofcommunications at times other than during readout of image signals.Therefore, the influence exerted onto the image signals, which are beingread out, by the wireless signals output from the control apparatus canbe reduced. Accordingly, the amount of noise that occurs in the imagesignals can also be reduced.

In the radiation imaging system of the present invention, aconfiguration may be adopted in which the second wireless communicatingsection: sets the signal strength of communications to a degree thatenables communication between the radiation imaging apparatus and thecontrol apparatus: decreases the signal strength of communications in astepwise manner, to obtain a signal strength at a step which is greaterthan or equal to a minimum signal strength that enables communicationsbetween the radiation imaging apparatus and the control apparatus; andsets the obtained signal strength as the signal strength ofcommunications during readout of the image signals. In this case,communications between the radiation imaging apparatus and the controlapparatus can be secured, and the influence exerted onto the imagesignals, which are being read out, by the wireless signals output fromthe control apparatus can be reduced further.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram that illustrates radiation imaging systemsaccording to first through fourth embodiments of the present invention.

FIG. 2 is a diagram that illustrates the interior structure of aradiation detecting cassette.

FIG. 3 is a block diagram that illustrates the circuit structure of aradiation detector.

FIG. 4 is a schematic block diagram of the radiation imaging system.

FIG. 5 is a block diagram that illustrates a portion of the innerstructures of a cassette transceiver of a radiation detecting cassetteand a console transceiver of a console.

FIG. 6 is a graph for explaining a method for setting gain levels andtransfer rates during readout in the radiation imaging system of thesecond embodiment.

FIG. 7 is a block diagram that illustrates the radiation imaging systemof the fourth embodiment.

FIG. 8 is a block diagram that illustrates a portion of the innerstructures of a cassette transceiver of a radiation detecting cassetteand a console transceiver of a console.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, four embodiments of radiation imaging systems will bedescribed with reference to the attached drawings. The radiation imagingsystem according to the fourth embodiment is the radiation imagingsystem of the present invention.

First, a radiation imaging system 10 according to a first embodimentwill be described.

FIG. 1 is a diagram that illustrates an operating room in which theradiation imaging system 10 is installed.

The radiation imaging system 10 is equipped with: an imaging apparatus22; a radiation detecting cassette 24; a display apparatus 26; and aconsole 28. The imaging apparatus 22 irradiates patients 14 withradiation X of a dosage according to imaging conditions. The radiationdetecting cassette 24 includes a radiation detector that detects theradiation X which has passed through the patients 14 and recordsradiation images of the patients 14. The display apparatus 26 displaysthe radiation images detected by the radiation detector. The console 28controls the operations of the imaging apparatus 22, the radiationdetecting cassette 24, and the display apparatus 26. Signals aretransmitted and received among the console 28, the imaging apparatus 22,the radiation detecting cassette 24 and the display apparatus 26 bywireless communications.

The imaging apparatus 22 is connected to a movable arm 30, to be movableto desired positions according to the portion of a patient 14 to beimaged, as well as to standby positions out of the way of physicians.Similarly, the display apparatus 26 is connected to a movable arm 32, tobe movable to positions at which physicians can easily observe obtainedradiation images.

FIG. 2 is a diagram that illustrates the interior structure of theradiation detecting cassette 24. The radiation detecting cassette 24 isequipped with a casing 34 which is transmissive with respect to theradiation X. A grid 38, for removing rays of the radiation X scatteredby the patient 14; a radiation detector 40, for detecting the radiationX which has passed through the patient 14 and for recording a radiationimage of the patient 14; and a lead plate 42, for absorbingbackscattered radiation X, are provided within the casing 34 in thisorder from the surface 36 of the casing 34 onto which the radiation X isirradiated. Note that the surface 36 of the casing 34 onto which theradiation X is irradiated may be configured to be the grid 38.

A battery 44, which is the power source of the radiation detectingcassette 24; a cassette control section 46, for driving and controllingthe radiation detector 40 by power supplied from the battery 44; and acassette transceiver 48, for transmitting radiation image signals readout from the radiation detector 40 and the like to the console 28 aswireless signals, and for receiving control signals and the like fromthe console 28, are also housed within the casing 34. Note that it ispreferable for lead plates to be provided on the cassette controlsection 46 and the cassette transceiver 48 toward the sides thereof thatface the surface 36 of the casing 34 onto which the radiation X isirradiated, in order to avoid damage due to irradiation by the radiationX. Although omitted from FIG. 2, a display section 85 and an operatingsection 86 are also provided on the radiation detecting cassette 24, asillustrated in FIG. 4. The display section 85 displays radiation imagesdetected by the radiation detector 40 and the like. The operatingsection 86 is provided to enable input of operating signals to theradiation detecting cassette 24. Further, a radiation detecting sensor87, for detecting the irradiated radiation X; and a signal processingsection 88, for administering predetermined signal processes on thesignals detected by the radiation detecting sensor 87 are provided. Acontrol section 84 generates control signals for automatic exposurebased on the signal detected by the radiation detecting sensor 87, andtransmits the control signals to the console 28 via the cassettetransceiver 48.

FIG. 3 is a block diagram that illustrates the circuit structure of theradiation detector 40. The radiation detector 40 is of a structure inwhich a photoelectric converting layer 51 formed by a substance thatsenses the radiation X and generates electric charges, such as amorphousselenium (a-Se) is provided on a TFT (Thin Film Transistor) array, inwhich TFT's 52 are provided in an array. The electric charges which aregenerated in the photoelectric converting layer 51 are accumulated in acharge accumulating capacitor 53. Then, each row of TFT's 52 aresequentially turned ON, to read out the electric charges accumulated inthe charge accumulating capacitor 53 as image signals. In FIG. 3, theconnective relationship between a single pixel 50 and a single TFT 52 isshown, and the structures that constitute other pixels 50 are omitted.Note that the structure of amorphous selenium changes at hightemperatures, and the function thereof deteriorates. Therefore, it isnecessary to use the photoelectric converting layer 51 within apredetermined temperature range. Accordingly, it is preferable for acooling means for cooling the radiation detector 40 to be providedwithin the radiation detecting cassette 24.

A gate line 54 that extends parallel to the row direction of the TFT's52 and a signal line 50 that extends parallel to the column direction ofthe TFT's 52 is connected to each TFT 52 which is connected to eachpixel 50 of the radiation detector 40. Each gate line 54 is connected toa line scanning drive section 58, and each signal line 56 is connectedto a multiplexer 66.

Control signals Von and Voff, for controlling the TFT's 52 arranged inthe row direction to be turned ON and OFF, are supplied to the gatelines 54 from the line scanning drive section 58. In this case, the linescanning drive section 58 is equipped with a plurality of switches SW1,for switching among the gate lines 54, and an address decoder 60 foroutputting a selection signal that selects one of the switches SW1.Address signals are supplied to the address decoder 60 from the cassettecontrol section 46.

Electric charges which are held in the charge accumulating capacitors 53for each pixel 50 flow to the signal lines 56, via the TFT's 52, whichare arranged in the column direction. These electric charges areamplified by amplifiers 62. The multiplexer 66 is connected to theamplifiers 62 via sample holding circuits 64. The multiplexer 66 isequipped with a plurality of switches SW2, for switching among thesignal lines 56, and an address decoder 68 for outputting a selectionsignal that selects one of the switches SW2. Address signals aresupplied to the address decoder 68 from the cassette control section 46.An A/D converter 70 is connected to the multiplexer 66, and radiationimage signals, which are converted to digital signals by the A/Dconverter, are output to the cassette control section 46.

FIG. 4 is a schematic block diagram of the radiation imaging system 10,constituted by the imaging apparatus 22, the radiation detectingcassette 24, the display apparatus 26 and the console 28.

The imaging apparatus 22 is equipped with: an imaging switch 72; aradiation source 74 that outputs the radiation X; a transceiver 76 thatreceives imaging conditions from the console 28 by wirelesscommunications, and transmits imaging completion signals and the like tothe console 28 by wireless communications; and a radiation sourcecontrol section 78 that controls the radiation source 74, based onimaging start signals supplied by the imaging switch 72 and imagingconditions supplied by the transceiver 76. Note that in cases thatautomatic exposure control is performed based on signals detected by theradiation detecting sensor 87 of the radiation detecting cassette 24,the control signal generated based on the signals detected by theradiation detecting sensor 87 is output from the cassette controlsection 46 to the console 28 via the cassette transceiver 48. Then, theconsole 28 outputs a control signal to the imaging apparatus 22. Thecontrol signal is input to the radiation source control section 78 viathe transceiver 76. Finally, the radiation source control section 78ceases emission of radiation from the radiation source 74.

The radiation detector 40, the battery 44, the cassette control section46, the cassette transceiver 48, and a power switch 45 are housed in theradiation detecting cassette 24. The power switch 45 is turned ON andOFF by control signals Ss output from the control section 84, to switchthe supply of power from the battery 44 to the radiation detector 40,the cassette control section 46, and the cassette transceiver 48 ON andOFF. The control section 84 outputs the control signals Ss to the powerswitch 45, based on control signals input thereto from the console 28via the cassette transceiver 48.

The cassette control section 46 is equipped with: an address signalgenerating section 80 that supplies the address decoder 60 of the linescanning drive section 58 of the radiation detector 40 and the addressdecoder 68 of the multiplexer 66 with address signals; an image memory82 for storing the radiation image signals which are read out from theradiation detector 40; and the control section 84 that controls theoperations of the address signal generating section 80, the image memory82, and the cassette transceiver 48. The control section 84 outputssignals indicating that radiation image signals are being read out fromthe radiation detector 40 to the cassette transceiver 48, as will bedescribed later. The signals output from the control section 84 are notlimited to those that indicate that radiation image signals are beingread out form the radiation detector 40. Various types of informationregarding the radiation detecting cassette 24, such as the operatingstate of the radiation detector 40, are output to the console 28 via thecassette transceiver 48. For example, a temperature sensor may beprovided in the radiation detecting cassette 24, and informationregarding the temperature may be output to the console 28 via thecassette transceiver 48. In addition, the control section 84 receivesvarious control signals issued to the radiation detecting cassette 24from the console 28 via the cassette transceiver 48, in addition to thecontrol signals Ss for turning the power switch 450N and OFF.

The display apparatus 26 is equipped with: a receiver 90 that receivesradiation image signals from the console 28; a display control section92 that controls the display of the received radiation image signals;and a display section 94 that displays radiation images based on theradiation image signals which have been processed by the display controlsection 92.

The console 28 is equipped with a console transceiver 96 that transmitsand receives necessary information, including radiation image signals,to and from the imaging apparatus 22, the radiation detecting cassette24, and the display apparatus 26 as wireless signals; an imagingcondition managing section 98 that manages imaging conditions which arenecessary for the imaging apparatus 22 to perform imaging operations; animage processing section 100 that administers image processes onradiation image signals transmitted from the radiation detectingcassette 24; an image memory 101 that records radiation image signals onwhich image processes have been administered; a patient informationmanaging section 102 that manages information regarding patients 14 whoare the subjects of imaging; and a cassette control section 103 thatoutputs various control signals to the radiation detecting cassette 24,such as the control signals for turning the power switch 450N, andreceives various types of information regarding the radiation detectingcassette 24, such as the operating state of the radiation detectingcassette 24.

Note that the term “imaging conditions” refers to conditions thatdetermine X-ray tube voltage, X-ray tube current, irradiation time, andthe like, such that the radiation X is irradiated at appropriate dosagesonto imaged portions of the patients. For example, the “imagingconditions” may be conditions such as “portion to be imaged” and“imaging method”. The term “patient information” refers to informationthat specifies each patient 14, such as the name, the sex, and thepatient ID number of the patients 14. Imaging ordering information thatincludes the imaging conditions and the patient information can be setat the console 28.

FIG. 5 is a block diagram that illustrates the inner structures of thecassette transceiver 48 of the radiation detecting cassette 24 and theconsole transceiver 96 of the console 28.

The cassette transceiver 48 of the radiation detecting cassette 24 isequipped with: a cassette transceiver control section 202 including amicrocomputer; an antenna 203; an antenna duplexer 205; a receivingsection 208; a transmitting section 210; and a variable gain amplifier212.

The receiving section 208 demodulates radio waves which are received bythe antenna 203 and input to the receiving section 208 via the antennaduplexer 205. The demodulated radio waves are output to the cassettetransceiver control section 202 as received signals. The transmittingsection 210 modulates and outputs radiation image signals, which areread out from the image memory 82 (refer to FIG. 4) and output from thecassette transceiver control section 202 at a predetermined transferrate.

The variable gain amplifier 212 amplifies the signals output from thetransmitting section 210 at a set gain, and outputs transmissionsignals. The gain level of the variable gain amplifier 212 is switchedaccording to control signals output from the cassette transceivercontrol section 202. The cassette transceiver control section 202 setsthe gain to be lower during readout of the image signals from theradiation detector 40, as indicated by signals from the control section84 (refer to FIG. 4), than the gain at times other than during readoutof image signals. Thereby, the signal strength of communications of thecassette transceiver 48 is set to be lower during readout of radiationimage signals than during times other than during readout of radiationimage signals. Note that the gain level of the variable gain amplifier212 during readout of the radiation image signals from the radiationdetector 40 is set to a value at which the wireless signals output fromthe cassette transceiver 48 do not influence the radiation image signalswhich are being read out. This gain level may be obtained in advance,and set at the cassette transceiver control section 202. Alternatively,noise levels may be detected from radiation image signals which arebeing read out, and the gain level may be set to that at which the noiselevel is lower than a predetermined threshold value.

Meanwhile, the console transceiver 96 is equipped with: a consoletransceiver control section 220 including a microcomputer; an antenna224; an antenna duplexer 226; a receiving section 228; and atransmitting section 230.

The receiving section 228 demodulates radio waves which are received bythe antenna 224 and input to the receiving section 228 via the antennaduplexer 226. The demodulated radio waves are output to the consoletransceiver control section 96 as received signals. The transmittingsection 230 modulates and outputs radiation image signals, which areoutput from the console transceiver control section 96.

Next, the operation of the radiation imaging system 10 of the firstembodiment will be described.

The radiation imaging system 10 is installed in an operating room 12,and used by a physician when radiation imaging of a patient becomesnecessary during surgery, for example. For this reason, the patientinformation of the patient 14 who is the subject of imaging isregistered in the patient information managing section 102 of theconsole 28 in advance, prior to imaging operations being performed. Inaddition, in the case that portions to be imaged and imaging methods arealso set in advance, these imaging conditions are registered in theimaging condition managing section 98 in advance. Surgery on the patient14 is initiated in a state in which the preparatory steps describedabove have been completed.

In the case that radiation imaging is to be performed during surgery,the physician or a radiological technician sets the radiation detectingcassette 24 at a predetermined position between the patient 14 and anoperating table 16 such that the surface 36 onto which radiation isirradiated faces the imaging apparatus 22.

Next, the physician or the radiological technician operates the console28 to output a control signal from the cassette control section 103 toturn the power switch 45 of the radiation detecting cassette 24 ON. Thecontrol signal is output from the console 28 via the console transceiver96. The control signal is received by the cassette transceiver 48 of theradiation detecting cassette 24, and output to the control section 84.The control section 84 outputs a control signal to the power switch 45to turn the power switch 450N. When the power switch 45 of the radiationdetecting cassette 24 is turned ON, various types of information, suchas the operating state of the radiation detecting cassette 24, areoutput from the control section 84 of the cassette control section 46.The information is output to the console 28 via the cassette transceiver4B.

Here, the signals that represent the various types of informationregarding the radiation detecting cassette 24 are output from thecassette transceiver control section 202 of the cassette transceiver 48to the transmitting section 210 at a predetermined transfer rate. Thesignals are modulated at the transmitting section 210, amplified by thevariable gain amplifier 212, then output to the console 28 via theantenna duplexer 205 and the antenna 203. At this time, the cassettetransceiver control section 202 is not receiving a signal from thecontrol section 84 that indicates that radiation image signals are beingread out from the radiation detector 40. Therefore, the gain level ofthe variable gain amplifier 212 is set at a level which is higher thanthat which is set during readout of radiation image signals, that is, again level which is used during standard wireless communications. Asdescribed above, the cassette transceiver control section 202 sets thegain level of the variable gain amplifier 212 at a higher level than thegain set during readout of radiation image signals, while signalsindicating that radiation image signals are being read out are not beingreceived from the control section 84.

Next, the imaging apparatus 22 is moved to a position that faces theradiation detecting cassette 24 and the imaging switch 72 is operated toperform an imaging operation.

The radiation source control section 78 of the imaging apparatus 22obtains imaging conditions for the portion of the patient 14 to beimaged from the image condition managing section 98 of the console 28,via the console transceiver 96 and the transceiver 76. The radiationsource 74 is controlled according to the obtained imaging conditions, toirradiate radiation X of a predetermined dosage onto the patient 14.

The radiation X which has passed through the patient 14 is irradiatedonto the radiation detector 40 after scattered rays are removed by thegrid 38 of the radiation detecting cassette 24. The photoelectricconverting layer 51 that constitutes the radiation detector 40 convertsthe radiation X into electric signals, and the charge accumulatingcapacitors 53 corresponding to each pixel 50 holds the electric signalsas electric charges (refer to FIG. 3).

Here, the radiation X which is irradiated toward the radiation detectingcassette 24 is detected by the radiation detecting sensor 87 provided inthe radiation detecting cassette 24 as well as by the radiation detector40. In the case that automatic exposure control is performed based onsignals detected by the radiation detecting sensor 87 of the radiationdetecting cassette 24, an automatic exposure control signal generatedbased on the signals detected by the radiation detecting sensor 87 isoutput from the control section 84 of the cassette control section 46 tothe console 28 via the cassette transceiver 48. At this time as well,the cassette transceiver control section 202 is not receiving a signalfrom the control section 84 that indicates that radiation image signalsare being read out from the radiation detector 40. Therefore, the gainlevel of the variable gain amplifier 212 is set at a level which ishigher than that which is set during readout of radiation image signals,that is, a gain level which is used during standard wirelesscommunications.

A control signal is output from the console 28 to the imaging apparatus22 in response to the automatic exposure control signal transmitted tothe console 28 from the radiation detecting cassette 24. The controlsignal is input to the radiation source control section 78 via thetransceiver 76. The radiation source control section 78 ceases emissionof radiation from the radiation source 74, based on the control signal.

After irradiation of the radiation X is ceased as described above, theelectric charges which are held in each of the charge accumulatingcapacitors 53 of the radiation detector 40 are read out according toaddress signals which are output from the address signal generatingsection 80 of the cassette control section 46 to the line scanning drivesection 58 and the multiplexer 66.

That is, the address decoder 60 of the line scanning drive section 58outputs a selection signal according to an address signal suppliedthereto the address signal generating section 80, to select one of theswitches SW. When the switch SW1 is selected, the control signal Von issupplied to the gate of the TFT 52 connected to the gate linecorresponding to the switch SW1. Meanwhile, the address decoder 68 ofthe multiplexer 66 outputs selection signals according to the addresssignals supplied thereto by the address signal generating section 80 tosequentially select the switches SW2. Thereby, the electric chargesignals which are held in the charge accumulating capacitors 53corresponding to each pixel 50 connected to the gate line 54 which hasbeen selected by the line scanning drive section 58 are sequentiallyread out via the signal lines 56.

The electric charge signals, which have been read out from the chargeaccumulating capacitors 53 corresponding to each pixel 50 connected tothe selected gate line 54 of the radiation detector, are amplified bythe amplifiers 62 connected to each of the signal lines 56. Theamplified signals are sampled by each of the sample holding circuits 64connected to the amplifiers 62, then supplied to the A/D converter 70via the multiplexer 66, where they are converted to digital signals. Theradiation image signals which have been converted to digital signals aretemporarily recorded in the image memory 82 of the cassette controlsection 46.

The address decoder 60 of the line scanning drive section 58sequentially switches the switch SW1 which is selected according to theaddress signals supplied thereto by the address signal generatingsection 80. Thereby, the electric charge signals, which are held in thecharge accumulating capacitors 53 corresponding to each pixel 50connected to the gate line 54 selected by the line scanning drivesection 58, are sequentially read out via the signal lines 56. Thesignals are recorded in the image memory 82 of the cassette controlsection 46 via the multiplexer 66 and the A/D converter 70.

The control section 84 of the cassette control section 46 sequentiallyreads out units of radiation image signals necessary for transmissionfrom the image memory 82 prior to radiation image signals correspondingto a single frame being recorded in the image memory 82. The read outunits of radiation image signals are output to the cassette transceiver48.

The cassette transceiver control section 202 outputs the units ofradiation image signals to the transmitting section 210 at apredetermined transfer rate. Then, the radiation image signals aremodulated by the transmitting section 210, amplified by the variablegain amplifier 212, then transmitted to the console 28 as wirelesssignals via the antenna duplexer 205 and the antenna 203.

Here, when radiation image signals are being read out from the radiationimage detector 40 as described above, a signal indicating that radiationimage signals are being read out is output from the control section 84of the cassette control section 46. This signal is input to the cassettetransceiver control section 202 of the cassette transceiver 48. Thecassette transceiver control section 202 outputs a control signal to thevariable gain amplifier 212 according to the signal, and lowers the gainlevel of the variable gain amplifier 212 to a preset gain level. Notethat the preset gain level of the variable gain amplifier 212 which isset during readout of the radiation image signals from the radiationdetector 40 is that at which the wireless signals output from thecassette transceiver 48 do not influence the radiation image signalswhich are being read out, as described previously.

After readout of the radiation image signals from the radiation detector40 is completed, the signal that indicates that readout is beingperformed is no longer output from the control section 84 of thecassette control section 46. At this time, the cassette transceivercontrol section 202 outputs a control signal to the variable gainamplifier 212 to increase the gain level to that which is used duringstandard wireless communications.

After readout of the radiation image signals from the radiation detector40 is completed, the radiation image signals which are still recorded inthe image memory 82 are amplified at the standard communication gainlevel, and output from the cassette transceiver 48.

The modulated signals transmitted to the console 28 are demodulated bythe console transceiver 96 as radiation image signals. Predeterminedimage processes are administered to the demodulated radiation imagesignals by the image processing section 100, then the processed imagesignals are correlated with the patient information registered in thepatient information managing section 102, and recorded in the imagememory 101.

Thereafter, the radiation image signals, which have undergone the imageprocesses, are transmitted from the console transceiver 96 to thedisplay apparatus 26. The display apparatus 26, which has received theradiation image signals through the receiver 90, controls the displaysection 94 with the display control section 92, and displays a radiationimage on the display section 94.

In the radiation imaging system according to the first embodimentdescribed above, the cassette transceiver 48 decreases the signalstrength of communications during readout of the radiation image signalsto be lower than the signal strength of communications at times otherthan during readout of the radiation image signals. Therefore, theinfluence exerted onto the radiation image signals, which are being readout, by the wireless signals output from the cassette transceiver 48 canbe reduced. Accordingly, the amount of noise that occurs in theradiation image signals can also be reduced.

Next, a radiation imaging system according to a second embodiment willbe described.

The radiation imaging system of the second embodiment is ofsubstantially the same configuration as the radiation imaging system ofthe first embodiment described above. However, the radiation imagingsystem of the second embodiment differs from that of the firstembodiment in the method by which the signal strength of the cassettetransceiver 48, that is, the gain level of the variable gain amplifier212, and the transfer rate of the signals output from the cassettetransceiver control section 202 during readout of radiation imagesignals, are determined.

In the radiation imaging system of the second embodiment, the signalstrength of the cassette transceiver 48, that is, the gain level of thevariable gain amplifier 212, and the transfer rate of the signals outputfrom the cassette transceiver control section 202 during readout ofradiation image signals, are determined after the power switch 45 of theradiation detection cassette 24 is turned ON. The gain level and thetransfer rate are determined prior to imaging operations of radiationimages are initiated.

First, a test signal is generated by the control section 84 of thecassette control section 46. The test signal is output to the cassettetransceiver control section 202 of the cassette transceiver 48. Next,the cassette transceiver control section 202 outputs the input testsignal to the transmitting section 210 at a predetermined transfer rate.The test signal is modulated by the transmitting section 210, amplifiedby the variable gain amplifier 212, then transmitted to the console 28as a wireless signal via the antenna duplexer 205 and the antenna 203.

At this time, the gain level of the variable gain amplifier 212 is setto a value (hereinafter, referred to as “first gain level”) at which thewireless signals output from the cassette transceiver 48 do notinfluence radiation image signals which are being read out. The firstgain level is set in the cassette transceiver control section 202 inadvance. The transfer rate when the test signal is output to thetransmitting section 210 is the slowest possible transfer rate(hereinafter, referred to as “first transfer rate”). The first transferrate is also set in advance.

The console 28 receives the test signal output from the radiationdetecting cassette 24 in the manner described above with the consoletransceiver 96. The received test signal is input to the cassettecontrol section 103.

The cassette control section 103 judges whether the signal strength ofthe input test signal is higher than a minimum signal strength(hereinafter, referred to as “minimum communicable condition”) which iscapable of being transmitted between the radiation detecting cassette 24and the console 28. Note that the minimum communicable condition is setin advance by the cassette control section 103.

In the case that the signal strength of the input test signal is higherthan the minimum communicable condition, the cassette control section103 outputs a signal (hereinafter, referred to as “communicationpossible signal”) indicating this fact to the radiation detectingcassette 24 via the console transceiver 96.

The radiation detecting cassette 24 receives the communication possiblesignal via the cassette transceiver 48, and the communication possiblesignal is input to the cassette transceiver control section 202. Whenthe communication possible signal is input, the cassette transceivercontrol section 202 sets the gain level of the variable gain amplifier212 to a second gain level which is lower than the first gain level. Atthe same time, the cassette transceiver control section 202 sets thetransfer rate to the transmitting section 210 to a second transfer rate,which is higher than the first transfer rate.

Then, the test signal is output again from the control section 84,output to the transmitting section 210 at the second transfer rate fromthe cassette transceiver control section 202, amplified at the secondgain level by the variable gain amplifier 212, and transmitted to theconsole 28 via the antenna duplexer 205 and the antenna 203.

The console 28 receives the test signal output from the radiationdetecting cassette 24 with the console transceiver 96 as describedabove. The received test signal is input to the cassette control section103.

The cassette control section 103 judges whether the signal strength ofthe input test signal is higher than the minimum communicable conditionagain.

In the case that the signal strength of the input test signal is higherthan the minimum communicable condition, the cassette control section103 outputs a communication possible signal to the radiation detectingcassette 24 via the console transceiver 96 again.

The radiation detecting cassette 24 receives the communication possiblesignal via the cassette transceiver 48, and the communication possiblesignal is input to the cassette transceiver control section 202. Whenthe communication possible signal is input, the cassette transceivercontrol section 202 sets the gain level of the variable gain amplifier212 to a third gain level which is lower than the second gain level. Atthe same time, the cassette transceiver control section 202 sets thetransfer rate to the transmitting section 210 to a third transfer rate,which is higher than the second transfer rate.

Then, the test signal is output again from the control section 84,output to the transmitting section 210 at the third transfer rate fromthe cassette transceiver control section 202, amplified at the thirdgain level by the variable gain amplifier 212, and transmitted to theconsole 28 via the antenna duplexer 205 and the antenna 203.

The console 28 receives the test signal output from the radiationdetecting cassette 24 with the console transceiver 96 as describedabove. The received test signal is input to the cassette control section103.

The cassette control section 103 judges whether the signal strength ofthe input test signal is higher than the minimum communicable conditionagain.

In the case that the signal strength of the test signal is lower thanthe minimum communicable condition, the cassette control section 103outputs a signal (hereinafter, referred to as “communication impossiblesignal”) indicating this fact to the radiation detecting cassette 24 viathe console transceiver 96.

The radiation detecting cassette 24 receives the communicationimpossible signal via the cassette transceiver 48, and the communicationimpossible signal is input to the cassette transceiver control section202. When the communication impossible signal is received, the cassettetransceiver control section 202 obtains the second gain level, which isgreater than the third gain level and satisfies the minimum communicablecondition. At the same time, the cassette transceiver control section202 obtains the second transfer rate, which is lower than the thirdtransfer rate. The second gain level and the second transfer rate areset as the gain level and the transfer rate to be employed forcommunications during readout of radiation images.

As described above, the gain level of the variable gain amplifier 212 isdecreased in a stepwise manner, and the transfer rate is increasedcorresponding to the stepwise decreases in gain level. When thecommunication impossible signal is output from the console 28, the gainlevel and the transfer rate of the immediately preceding step in thestepwise decrease and increase are set as the gain level and thetransfer rate to be employed for communications during readout ofradiation images.

Note that the transfer rates corresponding to the first through fourthgain levels illustrated in FIG. 6 are set in advance. The transfer ratesare set such that they do not adversely influence radiation imagesignals which are being read out, when radiation image signals areamplified at the gain level for each step and output from the radiationdetecting cassette 24 as wireless signals.

In the radiation imaging system of the second embodiment, during readoutof radiation image signals from the radiation detector 40, that is,while the signal that indicates that readout is being performed is beingoutput from the control section 84 of the cassette control section 46 tothe cassette transceiver control section 202, the gain level of thevariable gain amplifier 212 and the transfer rate of the cassettetransceiver control section 202 are set in the manner described above.When the signal indicating that readout is being performed ceases to beoutput from the control section 84 of the cassette control section 46,the gain level of the variable gain amplifier 212 and the transfer rateof the cassette transceiver control section 202 are set to a gain leveland a transfer rate which is used during standard wirelesscommunications.

According to the radiation imaging system of the second embodiment, thesignal strength of wireless communications during readout of theradiation image signals is decreased to a level which is close to theminimum signal strength that enables communications between theradiation detecting cassette 24 and the console 28. At the same time,the transfer is increased corresponding to the decrease of the signalstrength. Therefore, the influence exerted onto the image signals, whichare being read out, by the wireless signals output from the cassettetransceiver 48 can be reduced. Accordingly, the occurrence of noise inthe radiation image signals can be decreased. In addition, thetransmission time of the radiation image signals can be shortened.Accordingly, the processing efficiency of the apparatus can be improved.

Next, a radiation imaging system according to a third embodiment will bedescribed.

The radiation imaging system of the third embodiment is of substantiallythe same configuration as the radiation imaging system of the firstembodiment described above. However, the radiation imaging system of thethird embodiment differs from that of the first embodiment in that thesignal strength of the cassette transceiver 48, that is, the gain levelof the variable gain amplifier 212, is not decreased during readout ofradiation image signals from the radiation detector 40. Instead, thegain level of the variable gain amplifier 212 is kept constant, and thetransfer rate of the signals output from the cassette transceivercontrol section 202 of the cassette transceiver is varied.

Specifically, a signal indicating that radiation image signals are beingread out from the radiation detector 40 is output from the controlsection 84 of the cassette control section 46. This signal is input tothe cassette transceiver control section 202 of the cassette transceiver48. In response to this signal, the cassette transceiver control section202 decreases the transfer rate at which radiation image signals aretransferred to the transmitting section 210 to a preset speed. Note thatthe transfer rate during readout of radiation image signals from theradiation detector 40 is set such that wireless signals output from thecassette transceiver 48 do not adversely influence the radiation imagesignals which are being read out.

After readout of the radiation image signals from the radiation detector40 is completed, the signal that indicates that readout is beingperformed is no longer output from the control section 84 of thecassette control section 46. At this time, the cassette transceivercontrol section 202 increases the transfer rate at which radiation imagesignals are transferred to the transmitting section 210 to a transferrate which is used during standard wireless communications.

After readout of the radiation image signals from the radiation detector40 is completed, the radiation image signals which are still recorded inthe image memory 82 are output from the cassette transceiver controlsection 202 to the transmitting section 210 at the standardcommunication transfer rate.

As described in the first embodiment, various types of informationregarding the radiation detecting cassette 24 may be output to theconsole 28. At this time, the cassette transceiver 202 is not receivingthe signal from the control section 84 that indicates that radiationimage signals are being read out from the radiation detector 40.Therefore, the transfer rate at which radiation image signals aretransferred to the transmitting section 210 is set at the standardcommunication transfer rate, which is higher than the transfer ratewhich is set during readout of radiation images.

Automatic exposure control may be performed, by an automatic exposurecontrol signal generated based on signals detected by the radiationdetecting sensor 87 being output from the radiation detecting cassette24 to the console 28. At this time as well, the cassette transceivercontrol section 202 is not receiving a signal from the control section84 that indicates that radiation image signals are being read out fromthe radiation detector 40. Therefore, the transfer rate at whichradiation image signals are transferred to the transmitting section 210is set to be higher than that which is set during readout of radiationimage signals, that is, a transfer rate which is used during standardwireless communications.

According to the radiation imaging system of the third embodiment, thetransfer rate of the cassette transceiver control section 202 is set tobe lower during readout of radiation image signals from the radiationdetector 40 than the transfer rate at times other than during readout ofthe radiation signals. Therefore, the influence exerted onto the imagesignals, which are being read out, by the wireless signals output fromthe cassette transceiver 48 can be reduced. Accordingly, the amount ofnoise that occurs in the image signals can also be reduced.

Next, a radiation imaging system according to the fourth embodiment willbe described. The radiation imaging system of the fourth embodiment isthe embodiment of the present invention.

The radiation imaging systems of the first through third embodimentsdescribed above vary the signal strength and the transfer rate ofwireless communications from the radiation detecting cassette 24, takingthe adverse influence imparted onto the radiation image signals, whichare being read out from the radiation detector 40, by the wirelesssignals output from the radiation detecting cassette 24 intoconsideration. The radiation imaging system of the fourth embodimentfurther takes adverse influence imparted onto the radiation imagesignals, which are being read out from the radiation detector 40, bywireless signals output from the console 28 into consideration. That is,the radiation imaging system of the fourth embodiment takes the signalstrength of wireless communications from the console 28 intoconsideration. Note that control signals that may be output from theconsole 28 to the radiation detecting cassette 24 during readout ofradiation image signals from the radiation detector 40 include receptionerror signals. Specifically, radiation image signals are transmittedfrom the radiation detecting cassette 24 to the console 28 inpredetermined block units. The console 28 receives the radiation imagesignals in the block units, and judges whether the radiation imagesignals for each block have been correctly received by performing paritychecks and the like. If a reception error is detected for radiationimage signals in a certain block, a control signal that prompts theradiation detecting cassette 24 to resend the radiation image signals ofthe block, for which the error has been detected, is output. In theabove description, control signals are output from the console 28 to theradiation detecting cassette 24 only in cases that reception errors aredetected. Alternatively, a signal that indicates that reception wascompleted or a signal that indicates that a reception error has beendetected may be output from the console 28 to the radiation detectingcassette 24, for each block.

The radiation imaging system of the fourth embodiment is ofsubstantially the same configuration as the radiation imaging systems ofthe first through third embodiments described above. Therefore, adescription will be given mainly regarding structures which aredifferent from those of the first through third embodiments.

In the radiation imaging system of the fourth embodiment, a test signalgenerating section 104 that generates test signals is provided withinthe console 28, and a communication output judging section 89 isprovided within the radiation detecting cassette 24, as illustrated inFIG. 7.

In addition, a variable gain amplifier 232 that amplifies signals outputfrom the transmitting section 230 is provided in the console transceiver96 of the console 28, as illustrated in FIG. 8. The signal strength ofwireless signals output from the console transceiver 96 is varied, byvarying the gain of the variable gain amplifier 232.

Next, the operation of the radiation imaging system of the fourthembodiment will be described.

In the radiation imaging system of the fourth embodiment, the signalstrength of the console transceiver 96, that is, the gain level of thevariable gain amplifier 232, during readout of radiation image signalsfrom the radiation detector 40 is determined after the power switch 45of the radiation detection cassette 24 is turned ON. The gain level isdetermined prior to imaging operations of radiation images areinitiated.

Specifically, first, a test signal is generated by the test signalgenerating section 104 of the console 28. The test signal is output tothe console transceiver control section 220 of the console transceiver96. Next, the console transceiver control section 220 outputs the inputtest signal to the transmitting section 230 at a predetermined transferrate. The test signal is modulated by the transmitting section 230,amplified by the variable gain amplifier 232, then transmitted to theradiation detecting cassette 24 as a wireless signal via the antennaduplexer 226 and the antenna 224.

At this time, the gain level of the variable gain amplifier 232 is setto a value sufficiently high enough to enable communication between theconsole 28 and the radiation detecting cassette 24. This gain level isset in advance at the console transceiver control section 220.

The radiation detecting cassette 24 receives the test signal output fromthe console 28 in the manner described above with the cassettetransceiver 48. The received test signal is input to the communicationoutput judging section 89.

The communication output judging section 89 judges whether the signalstrength of the input test signal is higher than a minimum signalstrength (hereinafter, referred to as “minimum communicable condition”)which is capable of being transmitted between the radiation detectingcassette 24 and the console 28. Note that the minimum communicablecondition is set in advance by the communication output judging section89.

In the case that the signal strength of the input test signal is higherthan the minimum communicable condition, a signal (hereinafter, referredto as “communication possible signal”) indicating this fact is output tothe console 28 via the cassette transceiver 48.

The console 28 receives the communication possible signal via theconsole transceiver 96, and the communication possible signal is inputto the console transceiver control section 220. When the communicationpossible signal is input, the console transceiver control section 220slightly decreases gain level of the variable gain amplifier 232.

Then, the test signal is output again from the test signal generatingsection 104, output to the transmitting section 230 at the predeterminedtransfer rate from the console transceiver control section 220,amplified at the lower gain level by the variable gain amplifier 232,and transmitted to the radiation detecting cassette 24 via the antennaduplexer 226 and the antenna 224.

The radiation detecting cassette 24 receives the test signal output fromthe console 28 with the cassette transceiver 48 as described above. Thereceived test signal is input to the communication output judgingsection 89.

The communication output judging section 89 judges whether the signalstrength of the input test signal is higher than the minimumcommunicable condition again.

In the case that the signal strength of the input test signal is judgedto be higher than the minimum communicable condition, the communicationoutput judging section 89 outputs a communication possible signal to theconsole 28 via the cassette transceiver 48 again.

The console 28 receives the communication possible signal via theconsole transceiver 96, and the communication possible signal is inputto the console transceiver control section 220. When the communicationpossible signal is input, the console transceiver control section 220further decreases the gain level of the variable gain amplifier 232.

Then, the test signal is output again from the test signal generatingsection 104, output to the transmitting section 230 at the predeterminedtransfer rate from the console transceiver control section 220,amplified at the lower gain level by the variable gain amplifier 232,and transmitted to the radiation detecting cassette 24 via the antennaduplexer 226 and the antenna 224.

While the radiation detecting 28 keeps on outputting communicationpossible signals with respect to the test signals output from theconsole 28 in the manner described above, the console 28 sets the gainlevel of the variable gain amplifier 232 such that the gain levelgradually decreases. Further test signals are amplified at the decreasedgain levels, and output to the radiation detecting cassette 24.

In the case that the signal strength of the test signal is judged to belower than the minimum communicable condition, the communication outputjudging section 89 outputs a signal (hereinafter, referred to as“communication impossible signal”) indicating this fact to the console28 via the cassette transceiver 48.

The console 28 receives the communication impossible signal via theconsole transceiver 96, and the communication impossible signal is inputto the console transceiver control section 220. When the communicationimpossible signal is received, the console transceiver control section220 obtains the gain level which was set immediately previous to thegain level, which is set at that time. This gain level is set as thegain level (hereinafter, referred to as “readout gain level”) to be usedduring readout of radiation image signals from the radiation detector40. Note that the readout gain level is lower than the gain level whichis used at times other than during readout of radiation image signalsfrom the radiation detector 40.

During readout of radiation image signals from the radiation detector40, the control section 84 of the radiation detecting cassette 24 outputa signal indicating that readout is being performed. This signal isoutput to the console via the cassette transceiver 48.

Various control signals and radiation image signals are output from theconsole 28 to the radiation detecting cassette 24, the imaging apparatus22, and the display apparatus 26. While the signal that indicates thatreadout is being performed is being received by the console transceivercontrol section 220, the gain level of the variable gain amplifier 232is set to the readout gain level, which has been obtained in the mannerdescribed above. On the other hand, when the signal that indicates thatreadout is being performed is not being received by the consoletransceiver control section 220, the gain level of the variable gainamplifier 232 is set to a gain level which is used during standardwireless communications.

In the radiation imaging system of the fourth embodiment, during readoutof radiation image signals from the radiation detector 40, the signalstrength of wireless signals output from the console 28 is set to theminimum strength that enables communication between the console 28 andthe radiation detecting cassette 24. Therefore, the influence exertedonto the radiation image signals, which are being read out, by thewireless signals output from the console 28 can be reduced. Accordingly,the amount of noise that occurs in the radiation image signals can alsobe reduced.

Note that in the radiation imaging system of the fourth embodiment, thereadout gain was obtained in the manner described above. However, themethod by which the readout gain is obtained is not limited to thatwhich was described above. For example, a gain level at which thewireless signals output from the console 28 do not influence theradiation image signals which are being read out may be obtained inadvance, and set as the readout gain level. Alternatively, noise levelsmay be detected from radiation image signals which are being read out,and the gain level may be set to that at which the noise level is lowerthan a predetermined threshold value.

The radiation detector 40 which is housed in the radiation detectingcassette 24 of the radiation imaging systems of the first through fourthembodiments are those that directly convert the radiation X irradiatedthereon to electric signals with the photoelectric converting layer 51.However, the present invention is not limited to using radiationdetectors of this type. The radiation detector may be of the indirectconversion type. An example of such a radiation detector is that whichconverts radiation X irradiated thereon to visible light with ascintillator, then converts the visible light to electric signals usinga-Si (amorphous silicon) or the like (refer to Japanese Patent No.3494683).

In addition, the radiation detector 40 is a TFT readout type radiationdetector, that reads out electric charge signals using TFT's. However,the present invention is not limited to using radiation detectors ofthis type. The radiation detector may be of the optical readout type,that reads out accumulated electric charge signals by having readoutlight irradiated thereon (refer to U.S. Pat. No. 6,268,614).

1. A radiation imaging system, comprising: a radiation imagingapparatus, comprising: a radiation detecting section that generateselectric charges when irradiated with radiation which has passed througha subject, to record a radiation image of the subject; a readout sectionthat reads out image signals that represent the radiation image of thesubject from the radiation detecting section; and a first wirelesscommunicating section that reads out the image signals from the readoutsection and outputs the read out image signals as wireless signals; anda control apparatus, comprising: a second wireless communicating sectionthat receives the wireless signals output by the radiation imagingapparatus, and outputs predetermined control signals to the radiationimaging apparatus as wireless signals; the second wireless communicatingsection decreasing the signal strength of communications during readoutof the image signals by the readout section to be lower than the signalstrength of communications at times other than during readout of imagesignals and maintains communications during the image readout.
 2. Aradiation imaging system as defined in claim 1, wherein the secondwireless communicating section: sets the signal strength ofcommunications to a degree that enables communication between theradiation imaging apparatus and the control apparatus; decreases thesignal strength of communications in a stepwise manner, to obtain asignal strength at a step which is greater than or equal to a minimumsignal strength that enables communications between the radiationimaging apparatus and the control apparatus; and sets the obtainedsignal strength as the signal strength of communications during readoutof the image signals.
 3. A radiation imaging system as defined in claim1, wherein: the second wireless communicating section sets the signalstrength of communications during readout of the image signals to adegree at which the wireless signals output from the second wirelesscommunicating section do not influence the image signals which are beingread out.